It's a racing game, you gain speed by doing flips in the air.
The difficulty of the game is high for sure, you can lose speed very easily, but really hard to gain it back(or maybe it is because I suck).
So about the speed, I wanted to avoid having the player travel too fast for the reflexes to handle and adjusted the movement speed accordingly so any sort of acceleration or speed boost felt like it was hard-earned and extra-rewarding :P